This invention relates to a method of producing patterns of zigzag stitches with an electronic sewing machine of a type wherein each stitch pattern is stored in the form of an electronic stitch control information data which is selectively read out to generate a corresponding electronic stitch control signal.
An electronic sewing machine of a type described above has been generally known and is capable of producing various stitch patterns. In the electronic sewing machine a fabric feeding amount or pitch is generally controlled by a pulse motor via link mechanism to adjust an inclination of a fabric feed regulator. In this case, the minimum critical amount of the fabric feed is determined by the minimum angular step of the pulse motor and therefore the adjustment of the fabric feed amount is strictly limited to the integral times of the value determined by the minimum feeding amount, resulting in difficulties of minute adjustment of the fabric feed amount to meet the respective stitching requirements.
For example, such embroidery patterns as shown in FIG. 1 comprising a plurality of zigzag stitches must be densely produced with fabric feed amount being made substantially small.
FIG. 2 shows the pattern A of such embroidery stitch patterns, which is stitched in a conventional manner. More particularly, a predetermined feeding pitch P is provided to every stitch. If the minimum feeding pitch determined by the minimum angular step of the pulse motor is 0.2 mm, then the feeding pitch P can be selected to 0.2 mm, 0.4 mm, 0.6 mm--but can not be given values of 0.1 mm, 0.3 mm and 0.5 mm.
In order to obtain such a smaller adjusting step of the fabric feeding amount, it is required to more reduce the minimum angular step of the pulse motor. In this case, however, the control time of the pulse motor becomes longer and accordingly the sewing machine must be driven at a reduced speed, impairing efficiency of stitching operation.